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Date: Thu, 01 Jan 2009 23:22:16 -0600
From: Eric Sandeen <sandeen@...deen.net>
To: Takashi Sato <t-sato@...jp.nec.com>
CC: Andrew Morton <akpm@...ux-foundation.org>,
Christoph Hellwig <hch@...radead.org>,
"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
"dm-devel@...hat.com" <dm-devel@...hat.com>,
"viro@...IV.linux.org.uk" <viro@...IV.linux.org.uk>,
"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
"xfs@....sgi.com" <xfs@....sgi.com>,
"mtk.manpages@...glemail.com" <mtk.manpages@...glemail.com>,
"axboe@...nel.dk" <axboe@...nel.dk>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/3] freeze feature ver 1.14
In lieu of the timeout feature which was originally proposed, how
about access to an emergency un-freeze via magic sysrq, maybe
piggy-backed on emergency sync... something like this (not
tested or even built yet...), would this be a good compromise to
help save people from frozen roots?
-Eric
Index: linux-2.6/drivers/char/sysrq.c
===================================================================
--- linux-2.6.orig/drivers/char/sysrq.c
+++ linux-2.6/drivers/char/sysrq.c
@@ -151,6 +151,7 @@ static struct sysrq_key_op sysrq_reboot_
static void sysrq_handle_sync(int key, struct tty_struct *tty)
{
+ emergency_thaw();
emergency_sync();
}
static struct sysrq_key_op sysrq_sync_op = {
Index: linux-2.6/drivers/md/dm.c
===================================================================
--- linux-2.6.orig/drivers/md/dm.c
+++ linux-2.6/drivers/md/dm.c
@@ -1477,7 +1477,7 @@ static void unlock_fs(struct mapped_devi
if (!test_bit(DMF_FROZEN, &md->flags))
return;
- thaw_bdev(md->suspended_bdev, md->frozen_sb);
+ thaw_bdev(md->suspended_bdev, md->frozen_sb, 0);
md->frozen_sb = NULL;
clear_bit(DMF_FROZEN, &md->flags);
}
Index: linux-2.6/fs/buffer.c
===================================================================
--- linux-2.6.orig/fs/buffer.c
+++ linux-2.6/fs/buffer.c
@@ -259,13 +259,29 @@ struct super_block *freeze_bdev(struct b
EXPORT_SYMBOL(freeze_bdev);
/**
+ * emergency_thaw -- force thaw every filesystem
+ *
+ * Used for emergency unfreeze of all filesystems via SysRq
+ */
+void emergency_thaw(void)
+{
+ struct super_block *sb;
+
+ list_for_each_entry(sb, &super_blocks, s_list) {
+ if (sb->s_bdev)
+ (void)thaw_bdev(sb->s_bdev, sb, 1);
+ }
+}
+
+/**
* thaw_bdev -- unlock filesystem
* @bdev: blockdevice to unlock
* @sb: associated superblock
+ * force: force unfreeze regardless of freezer count
*
* Unlocks the filesystem and marks it writeable again after freeze_bdev().
*/
-int thaw_bdev(struct block_device *bdev, struct super_block *sb)
+int thaw_bdev(struct block_device *bdev, struct super_block *sb, int force)
{
int error = 0;
@@ -275,7 +291,11 @@ int thaw_bdev(struct block_device *bdev,
return -EINVAL;
}
- bdev->bd_fsfreeze_count--;
+ if (force)
+ bdev->bd_fsfreeze_count = 0;
+ else
+ bdev->bd_fsfreeze_count--;
+
if (bdev->bd_fsfreeze_count > 0) {
if (sb)
drop_super(sb);
Index: linux-2.6/fs/ioctl.c
===================================================================
--- linux-2.6.orig/fs/ioctl.c
+++ linux-2.6/fs/ioctl.c
@@ -449,7 +449,7 @@ static int ioctl_fsthaw(struct file *fil
return -EINVAL;
/* Thaw */
- return thaw_bdev(sb->s_bdev, sb);
+ return thaw_bdev(sb->s_bdev, sb, 0);
}
/*
Index: linux-2.6/fs/xfs/xfs_fsops.c
===================================================================
--- linux-2.6.orig/fs/xfs/xfs_fsops.c
+++ linux-2.6/fs/xfs/xfs_fsops.c
@@ -634,7 +634,7 @@ xfs_fs_goingdown(
if (sb && !IS_ERR(sb)) {
xfs_force_shutdown(mp, SHUTDOWN_FORCE_UMOUNT);
- thaw_bdev(sb->s_bdev, sb);
+ thaw_bdev(sb->s_bdev, sb, 0);
}
break;
Index: linux-2.6/include/linux/buffer_head.h
===================================================================
--- linux-2.6.orig/include/linux/buffer_head.h
+++ linux-2.6/include/linux/buffer_head.h
@@ -171,7 +171,8 @@ void __wait_on_buffer(struct buffer_head
wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
int fsync_bdev(struct block_device *);
struct super_block *freeze_bdev(struct block_device *);
-int thaw_bdev(struct block_device *, struct super_block *);
+void emergency_thaw(void);
+int thaw_bdev(struct block_device *, struct super_block *, int);
int fsync_super(struct super_block *);
int fsync_no_super(struct block_device *);
struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block,
--
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